Outdoor Air Pollution: From Evidence to Comprehensive Action
The following is intended as a briefing paper which provides an introductory examination of the priority problem of outdoor air pollution, with a specific emphasis on its significance to global human health. The paper shall examine outdoor air pollution’s direct human health impacts, the background and scope of outdoor air pollution in the political context of today’s world, and historical policy responses. It will then examine major current national and international policy efforts to address the problem. Finally, it shall make basic policy recommendations with the intent of guiding future discussion towards the main theme of establishing a global, synchronous, and comprehensive response at the current strategic transition point in time.
Defining Outdoor Air Pollution
This paper examines “outdoor air pollution,” also known as “ambient air pollution,” defined here as: the contamination of the outdoor environment by any chemical, physical, or biological agents and particles which alter the normal state and characteristics of the atmosphere, with a specific emphasis on human sources and the urban environment.  The paper shall make extensive use of statistics and measurements provided by studies based on population exposures to concentrations of particulate matter (PM) and key pollutants known to contribute to outdoor air pollution. 
In general, outdoor air pollution stems from particles emitted from two categories of sources: natural sources and human activities (anthropogenic).  The natural sources include, but are not limited to: volcanoes, dust, and even vegetation.   Of more immediate concern is the battery of human sources which are controllable and contribute heavily to outdoor air pollution. These include in all of its forms: the combustion of fossil fuels (domestic heating, generating power, motor vehicles, cooking) industrial and agricultural activity, waste incineration, and biomass burning. . It is of particular note that in urban locales, fuel combustion conducted by mobile sources, i.e. vehicles, generate more than 50% of measured PM concentrations. 
The sources of outdoor air pollution act to contaminate the environment by releasing a variety of particles and agents that are of particular concern to human health and well-being. (fig.1) Some of the key chemical agents released include: carbon monoxide, sulfur dioxide, and nitrogen oxides.  Individual particles can remain suspended in the air and form complexes as “particulate matter” or form chemical compounds like ozone, contributing further to outdoor air pollution and damage to human health.  
The Human Toll
A key step to addressing and understanding the public health issue of outdoor air pollution stems first from a broad understanding of outdoor air pollution’s general impacts on human health. The most fundamental point is that outdoor air pollution creates an environment that weakens and damages people’s health, and makes them susceptible to dangerous diseases and exacerbates respiratory conditions.  On the global scale, WHO estimates that urban outdoor air pollution results in 1.3 million deaths worldwide per year.  The 2002 World Health Report indicates that outdoor air pollution was responsible for 1.4% of total worldwide mortality and 0.5% of all DALYs.  Updated comprehensive studies in 2010 found outdoor air pollution to be responsible for 3.2 million premature deaths and 74 million healthy life years lost (DALYs) and now ranks outdoor air pollution as among the top 10 most important health risks worldwide.  Tragically, research has firmly established that children and the elderly worldwide are particularly susceptible to the effects of outdoor air pollution.  Children 5 years and under were shown to have accounted for 3% of deaths caused by outdoor air pollution and 12% of DALYs.  About 24,000 children around the world die prematurely due to outdoor air pollution. . Children spend more time outside than adults, inhaling more pollutants per kg, and suffering more physiological damage due to ongoing lung development which increases their vulnerability to the air pollutants’ effects.  Significant exposure to outdoor air pollution impairs children’s lung growth and development, affecting them into adulthood.  The elderly are severely affected as well. Nearly 81% of deaths caused by outdoor air pollution and 49% of related DALYs were found to have occurred in people aged 60 and older.  Furthermore, people living in middle income countries of the world are likely to be particularly affected by outdoor air pollution. 
On a smaller scale, outdoor air pollution increases the occurrence of chronic bronchitis, acute respiratory illness, exacerbates asthma and coronary disease, and severely weakens lung function.  It can also weaken heart function and promote atherogenesis.  In addition, outdoor air pollution has been linked to adverse birth outcomes.  The inhaled particles and pollutants are associated with increased risk for all causes of mortality, particularly those stemming from the cardiorespiratory category. (fig.2)  Perhaps most interestingly, lower levels of outdoor air pollution based on lower particulate matter levels were associated with longer lifespans and fewer hospital admissions.  In a study consisting of four decades of data, from across 51 metropolitan areas across the United States, reductions in air pollution levels contributed to as much as a 15% increase in overall human life span, with the same level of impact associated despite fluctuations in demographics, socioeconomics, and other proxy variables, like smoking.  Especially worrisome is the fact that human morbidity is associated with any detectable level of PM concentration, not just high concentrations.  Thus outdoor air pollution exhibits a disturbing ubiquity and ability to penetrate and damage every part of human society regardless of wealth or assumed cleanliness of a particular area.
Even a cursory examination of the serious health impacts that outdoor air pollution causes from the global to the individual scale demonstrates the heavy health burden the issue is responsible for. From a health perspective alone, it is too dangerous and pervasive to ignore.
The Context and Scope of the Problem
Outdoorairpollution’sriseemergesduringakeytransitionpointinhumantime. Forthefirst time in human history, the majority of humans now dwell in cities, as opposed to rural areas, and this shift continues to increase as population rises.  By 2030, 6 out of every 10 humans are projected to be dwelling in cities, and by 2050, this is expected to increase to 7 out of 10.  This is likely to aggravate the effect of urban outdoor air pollution on human populations. With urbanization occurring throughout much of the world, key nations are experiencing notable rates of industrialization and development, including the well-known BRICS (Brazil, Russia, India, China, South Africa) countries.  (fig.3) By 2050 the world economy is projected to quadruple in size, largely as a result of the rapid growth of developing nations. Naturally coupled with this rapid growth is a projected tremendous increase in consumption, particularly in the worldwide energy sector.  Energy use is predicted to increase by 80%, and fossil fuel use, consisting of combustible energy sources like coal and oil which contribute heavily to outdoor air pollution, is projected to still account for 85% of total energy use by 2050. 
Although developed nations have successfully reduced levels of outdoor air pollution to a noticeable degree, much of the impact of the outdoor air pollution is now observed in the growing megacities of the developing nations.  (fig.4) The developing nations’ rapid urbanization and development are worsening the degree of pollution.  Many low and middle income countries have yet to implement the type of regulations on outdoor air pollution seen in developed nations because they do not see the immediate impacts from outdoor air pollution and prioritize industrialization.  India and China alone, with their rapid development, now account for two thirds of the global burden of disease from outdoor air pollution, but they continue to rely on unclean fuel sources and polluting industrial systems that exist on a widespread scale.  How to convince developing nations to adopt and prioritize the management of outdoor air pollution as part of a worldwide effort to combat the problem while providing them the fair opportunity to develop without incurring exorbitant costs is a key debate to consider. Indeed, developing nations have merit in demanding the same full ability to industrialize that the developed nations once had, without the “handicaps” of environmental regulation that are now urged upon them.
Regardless of fairness, outdoor air pollution is not a regional problem and must no longer be seen as such. By 2050, outdoor air pollution is projected to become the world’s leading cause of environmentally linked deaths worldwide at over 3.5 million annually.  (fig.5) It is still viewed as a problem to be addressed on a limited scale, and not on a global basis, despite the fact that pollution has no borders.  It is important to reiterate and embrace the classic concept of “the Commons” to understand the problem of outdoor air pollution.  Multiple actors acting in self-interest can come to destroy a shared natural resource, in this case, the clean atmosphere.  .In this same vein, individual nations, failing to restrain their own outdoor air pollution levels, can contribute to the global degradation of a common good—the outdoor air environment. Outdoor air pollution has no borders, and can easily originate from one country to impact another. There are many well known cases of the long range transport of air pollutants from one individual nation affecting several others, even across the planet. Fire burning practices in Indonesia in 2010 caused smog and thick haze in several neighboring nations.  The Chernobyl nuclear disaster of 1986 is widely known to have spread radioactive particles in the air all throughout Europe.  The Fukushima Nuclear Disaster is known to have spread radioactive particles as far as Seattle, Washington.  Thus outdoor air pollution generated in one region has consequences throughout the world, and any discussion or examination of outdoor air pollution requires these trends and concepts for context and understanding. Any nation has the right to prioritize industrialization or any other policy; however, no such decision should be made without a full understanding of the problem or without considering this strategic point in human history at which outdoor air pollution is gaining momentum. These trends are especially important to consider in the examination of outdoor air pollution because they imply that it will worsen exponentially in the future, and on a widespread, global scale.
Past Disasters, Current Policies: The Initial Impetus for Action
Historically, in the developed world, little attention was paid to outdoor air pollution, and even fewer effective policies were adopted to address the issue until three key incidents occurred that forced the public and policy makers to acknowledge the consequences of allowing outdoor air pollution to reign free. These three incidents are generally regarded as the “classic” examples of the results of severe outdoor air pollution and poor regulation: Meuse Valley, Belgium (1930), Donora, United States (1948), and London, England (1952).   In the Meuse Valley Incident, industrial pollution along with stable atmospheric conditions resulted in the accumulation of outdoor air pollutants like sulfur dioxide and fluoride, resulting in 60 deaths and a mortality rate 10 times the norm.  The Donora, Pennsylvania incident also saw the confluence of stagnant weather conditions and industrial pollution released into the air to result in the deaths of 20 people, and a death rate six times the norm.  The Donora incident is notable for being one of the earliest wide-scale publically recognized examples of extreme air pollution.  The London Fog of 1952 resulted from stable atmospheric conditions and continuing pollution from the burning of coal in homes and industries throughout London.  The thick pollution was initially mistaken for the normal fogs that settled over London until it became clear it was actually having negative effects on the populace.  The accumulation of outdoor air pollution eventually resulted in over 12,000 premature deaths.  The smog observed in the London Fog of 1952 was noted as being so thick that many forms of transportation simply had to be stopped out of concern for safety, and some public performances were shut down due to intolerable conditions for the audience and performers.  These incidences are widely regarded as key events which stimulated serious study of outdoor air pollution’s effects on human health.  Perhaps more importantly, the incidences acted as an impetus for legislation regulating outdoor air pollution and represented the beginning of serious efforts to address outdoor air pollution.  They also provide a subtle warning for the issue of outdoor air pollution today. Many environmental issues are often ignored or disregarded until the situation deteriorates to an extreme point where humans are being noticeably harmed. Considering the strategic point in time and development at which society finds itself in regards to outdoor air pollution today, the three classic outdoor air pollution incidences which occurred six to eight decades ago still hold important lessons to keep in mind for now and the decades to come.
Following these disastrous incidences, various pieces of legislation were passed in particular nations of the developed world to address outdoor air pollution from the national scale down to the individual city; these laws have been revised and updated as time has progressed. Following the London Fog, the United Kingdom passed the Clean Air Act of 1956, banning the emission of black smoke and forcing urban residents and citizens to use cleaner burning fuels.  In the United States, the first major legislation to address outdoor air pollution was the Clean Air Act of 1955, which provided federal funding for research on outdoor air pollution and its sources.  This was followed by the Clean Air Act of 1963, which authorized a federal program headed by the US Public Health Service to address the issue of outdoor air pollution.  The latest version of the laws in the US is the Clean Air Act of 1990, which expanded national air quality standards, and authorized new measures to control 189 dangerous pollutants.  (fig.6) The establishment of national air quality standards was a particularly important step in that they provided benchmark values to both legislators and the public to actively work towards or maintain. Various other nations have their own major regulations and standards regarding outdoor air pollution, such as the United Kingdom’s Clean Air Act of 1993 and Canada’s Environmental Protection Act, which undergo periodic updates.  The European Union also established updated and combined standards in 2008 for outdoor air pollution, called the “New Air Quality Directive.”  All the examples of developed nation’s policies on outdoor air pollution exhibit a strong emphasis on multipronged approaches to addressing outdoor air pollution, reflecting its complex web of sources and causes.
Much of the developing world, however, still lags in aggressive legislation to address environmental issues affecting human health, particularly outdoor air pollution.  The overall problem stems from a failure to place environmental issues on a high priority; rapid population growth, industrialization, development, and energy demand, are prioritized along with war, natural disasters and a battery of other major problems typically facing developing nations; these are also resource intensive and time consuming to manage.  This diverts funds and political will to deal with outdoor air pollution and other key environmental issues with real impacts on a nation’s populace. In particular, industrialization is occurring in the developing world at three times the rate it did during the industrial revolution era of the western nations, and a thorough legal framework to regulate the explosive growth is often lacking.  In a chilling reminder of the 1952 London Fog, the Chinese capital of Beijing experienced outdoor air pollution levels of PM2.5, peaking at 1000 micrograms per cubic meter of air in January 2013; current WHO guidelines allow for 25 micrograms as an acceptable level.  PM2.5 is an especially dangerous category of particulate matter because it represents particles small enough to enter the lungs and the bloodstream, causing damage.  Despite these different priorities, the burden of outdoor air pollution will only increase drastically in both the developing and developed nations; it therefore implies the need for a balanced approach between regulation and development. Outdoor air pollution and related environmental issues must be weighed equally with growth, development, and other factors in order for a developing nation to maintain healthy, sustainable development.
Following the three classic incidences of outdoor air pollution, the widespread adoption of serious legislation capable of regulating and impacting outdoor air pollution has had noticeable results in developed nations from the national level down to the individual city level worldwide.  Key megacities in the United States and Europe all have now seen a steady decrease in outdoor air pollution levels.  In the United States, outdoor air pollution based on the emission and presence of key pollutants like Carbon Monoxide, Lead, and PM levels have all steadilydeclined since the 1980s. (fig. 7, 8) The demonstrable decrease in the amount of key pollutants on the national level reveals that serious legislation, in this case embodied by the Clean Air Acts, can have real impact on the magnitude of outdoor air pollution. Important to such legislation, however, is the presence of real authority to enforce it, and standards by which to work by. Particularly impressive in the case of the United States is the achievement of decreased levels of outdoor air pollution, specifically of key emissions known to stem largely from industrial or mobile sources, while maintaining continued economic growth. (fig. 9) This holds important ramifications for the developing world, indicating that increased regulation in regards to outdoor air pollution and continued economic and industrial growth are not entirely mutually exclusive. However, even the developed nation’s most progressive laws are still not aggressive enough to fully combat outdoor air pollution; in the United States alone, at least 124 million people, or roughly thirty percent of the US population, dwell in counties with air pollution levels exceeding acceptable national standards.  Some of the progress made by sweeping legislation has also been dampened by new sources of emissions or air pollution indoors. 
Beyond individual developed nations, progress has been made at the international level, but it is severely lacking in providing either a direct or an in-depth response to addressing the rapidly worsening issue of outdoor air pollution. There are several key works in the effort to address outdoor air pollution at the international level. Interestingly, very little international cooperation has been conducted for the direct purpose of addressing outdoor air pollution on a global scale; rather much of it has been related to international efforts to cooperate on curbing the effects of climate change.  A connection, however, lies in the fact that many of the sources of outdoor air pollution release pollutants also responsible for climate change.  The 1992 UN Framework on Climate Change was the first significant attempt at an international legal outline which established an overall framework for inter-government action on climate change.  Specifically, it recognized that a clean atmosphere was a common good and that among other factors, industrial activity resulted in the emission of pollutants that could contribute to climate change.  The next major work of international cooperation was the 1997 Kyoto Protocols, in which signatories agreed to make commitments to take measures to reduce emissions of six key gasses: carbon dioxide, methane, nitrous oxide, sulphur hexafluoride, hydrofluorocarbons, and perfluorocarbons.   International efforts to coordinate a global effort at reducing particular pollutants through the Kyoto Protocol, however, were dampened by the refusal of the United States to commit to the protocol’s goals.  The refusal of the United States to commit to the Kyoto Protocols represents a key problem in convincing developing nations to increase their prioritization of issues like outdoor air pollution; indeed developed nations must participate fully in international efforts in order to lend credibility to the problem’s growing threat as well as to foster truly cooperative international efforts. The 2001 Marrakesh Accords were significant in that they directly established an agreement to explore ways of transferring advanced technologies from the developed nations to the developing nations to help accomplish the goals set in the Kyoto Protocols.  This represents some of the first serious work on establishing binding means of bringing the developing nations to the same financial and technical capability of the developed nations. Furthermore, it sent a powerful message of commitment to environmental goals regardless of national development. Finally, the 2012 UN Climate Change Conference at Doha agreed to extend the Kyoto Protocol to 2020 and establish a pathway for a successor agreement to be implemented by then.  The Kyoto Protocol and its successor agreements are representative of the first international agreements to address outdoor air pollution on any significant level. Although their ultimate goal is
broader in scope than simply outdoor air pollution’s effects on human health, they are nonetheless critical forestablishingamodelbywhichinternationalactioncanbeconductedonoutdoorairpollution. They provide important policy examples to study and understand in order to coordinate future large scale international efforts directly aimed at reducing worldwide emissions and the levels of other dangerous outdoor air pollutants harming human health, like those seen in figure 1. On a lesser scale, international organizations like the World Health Organization have contributed by emphasizing the concept of integrating the concern for health in both international and national energy laws and programs.  Furthermore, WHO continues to monitor air pollution levels throughout the world while collecting huge amounts of data from all around the planet concerning the problem.  WHO’s most significant contribution, however, could be considered the publication of its Air Quality Guidelines to educate nations about air pollution levels at which human health is jeopardized.  The guidelines also provide interim targets for countries with high air pollution levels to reach.  WHO’s contribution of the international standards are also important in that they help create a narrative in which the international community is encouraged to strive against outdoor air pollution in incremental amounts. This presents hope for more aggressive action in the future, and even immediate steps towards step-wise action from developing nations.
What direction international and national policies should take concerning outdoor air pollution in the future is an issue of tremendous importance with great complexity. Even a general understanding of the issue and its context, however, can help provide some basic recommendations and guidelines for precautionary future policy:
1. Official and unofficial recognition on the national and international level of the serious upcoming threat presented by outdoor air pollution to human health and the common good: the clean atmosphere.
The international community must embrace the fact that the world is now at an important, strategic crossroad in time. Much of the world is experiencing rapid growth in population, industry, and economic development. (fig.3) Although this growth is beneficial in many ways, it also means the aggravation of outdoor air pollution, to the point that it is projected to become the leading cause of environmentally related deaths around the world by 2050. (fig.5). The majority of deaths and human health burden will be directly experienced in the developing world; despite this, the developed world has just an equal burden of tackling outdoor air pollution because current legislation is still inadequate and because the pollutants involved have no boundaries and can spread across borders.  The international community must embrace the idea of the commons, particularly as it prepares to enter a new era in which there is larger population, higher energy use globally, increased consumption, and increased interdependence.
2. Increased emphasis on international cooperation with the direct purpose of addressing outdoor air pollution, emphasizing long-term, sustainable legislative and technical solutions.
Current international cooperation on outdoor air pollution is limited to pollutants to be regulated by the Kyoto protocol, scheduled to last until 2020.  This international cooperation, however, was designed ultimately to target climate change. No real international framework exists to directly address the issue of outdoor air pollution on a comprehensive, global scale and this must be rectified during this strategic period. The Doha conference and the Kyoto protocols provide an important example by which new international efforts could be made to address outdoor air pollution. Developed nations, however, must take the lead by committing to key goals of a new work on outdoor air pollution. Such commitment would lend the necessary credibility to any international effort on the problem, and provide much needed political force and direction for the international community. The United States’ refusal to commit to the Kyoto protocols, for example, has acted as a divisive factor in international climate change efforts. The US, along with other developed nations, have a special obligation to lead by example on outdoor air pollution, particularly considering that such nations are a major contributor of harmful emissions. 
Just as important is the fact that international efforts to combat environmental issues have met some success; the Montreal Protocol, which was an international treaty designed to eliminate the use of CFCs and other chemicals which destroy the ozone has made noticeable progress.  It has achieved enough progress that scientists project a slow but nearly full recovery of the ozone by the middle of the 21st century.  Thus in an analogous vein, an aggressive and comprehensive protocol designed to address outdoor air pollution is not only feasible, but likely to yield measureable results, provided the political will is available.
3. Increased sharing of information between governments and study of aid for developing nations
Although there is want for serious international cooperation in regards to outdoor air pollution, various nations have seen smaller scale solutions implemented with notable success. Some of these novel solutions and working policies are important measures that should be shared with other nations, so that they too might consider implementing a successful variation of it. Even procedures that failed provide important sources of knowledge and allow for revised and improved future policies. London’s efforts on traffic control beginning February 2003 were originally aimed at reducing congestion in London; surprisingly, however, they revealed that despite reductions in road traffic emissions, outdoor air pollution remained mostly unchanged, indicating that other background factors were involved in the case of London’s outdoor air pollution.  . Notable successful policies have been seen in both developed and developing nations. An example includes the city of Bogota, Colombia, which adopted a multipronged approach including improved public transportation and the promotion of alternative transportation in the city, resulting in a 40% reduction in PM emissions in one year.  The key Indian city of Delhi began a comprehensive, gradual transition to compressed natural gas fuel beginning in April 1995 to November 2002 which included the mandatory fitting of catalytic convertors, complete removal of lead in petrol, and increased legal restrictions on automobiles in the city.  PM10, carbon monoxide, and sulfur dioxide levels all fell significantly, but some of the gains now appear to be offset by the tremendous number of vehicles on the road and also an increase in diesel automobiles.  Thus these type of case studies implemented on the local levels across the world must be the studied, analyzed, compiled, and shared between nations so that they can develop tailored policies most effective for their own cities and regions.
It is also important to increase the discussion of aid for developing nations; although the 2001 Marrakech accords established an early dialogue on how to transfer technology to developing nations to address outdoor air pollution, the issue is still divisive in developed nations.  The international community must continue to study the issue and explore the systematic means of transferring technologies to developing nations as well as other forms of aid, such as subsidies for clean air technologies in developing nations. For example, the full benefits from the transition from petrol to CNG in Delhi, India, are suspected to have been offset in part by poor technology.  A framework on aid for developing nations in regards to outdoor air pollution could help prevent such backward progress and help motivate developing nations with a task that can prove to be difficult even for wealthier, developed nations.
4. Expansion of multifaceted regulations from the federal to city level emphasizing the integration of health considerations into energy laws and programs, industrial activities, and vehicular emissions
After the three classic incidents of outdoor air pollution, the developed nations’ implementation of national laws regulating such pollution have gradually yielded strong results. (fig.6,7,8) In the case of the United States, increased regulations in the form of the Clean Air Acts did not necessarily mean decreased vehicle use or economic growth. (fig. 8) In fact population, vehicle use, and economic growth continued to increase. Clearly the case of individual developing nations cannot be directly compared with those struggling with outdoor air pollution in the developing world. The case of the United States does, however, demonstrate that increased outdoor air pollution regulation need not be mutually exclusive with development and growth. Examination of particular case studies reveals how outdoor air pollution is most affected by comprehensive legislation that integrates public health considerations while regulating a broad spectrum of emission sources. During the 2008 Olympics in Beijing, China, studies on the government efforts to improve outdoor air quality in the city including increased use of natural gas, relocation of polluting industries, and improvement of public transportation found that they yielded rapid, significant, and demonstrable improvements in air quality and public health. They also provided direct evidence for the use of public health policies to improve air quality.  In a similar vein, during the 1996 Olympic Games in Atlanta, Georgia, the city reduced emissions by aggressively encouraging public transportation, improving public transportation, closure of areas to private vehicles, and telecommuting.  Such policies resulted in a 28% reduction in ozone concentration, and a 42% decrease in acute asthma events.  Although these are examples of dramatic short-term action smaller in scope, the Beijing and Atlanta Olympic Games provide a type of proof of concept. Even short term but aggressive, broad regulation allows for dramatic results, and almost immediate improvements in health; thus regulation of outdoor air pollution must be implemented as soon as possible and at every level. In fact, even at the federal level in the United States, emission control strategies involve AQM, or “air quality management” which emphasizes involving multiple branches of government and local communities in order to tailor and streamline efforts to curb outdoor air pollution as rapidly as possible.  Thus it is apparent that in cases of success, regulation was effective because it worked on a comprehensive scale, integrating health considerations into a wide variety of fields including industrial placement and activities, vehicular emissions, energy policy, and even cultural considerations from the national to the local level. In any nation, such sweeping legislation would indeed be difficult to pursue; however, it could be enacted in progressive steps each of which expands in scope gradually, much like the Clean Air Acts in the United States. (fig. 5)With each progressive step, savings in health care costs and concrete evidence demonstrating improvement could be used to increase political support for expanded legislative efforts.
5. Nationwide education on the inverse relationship between outdoor air pollution and human health, and increased funding for research on outdoor air pollution and control mechanisms.
The health impacts of outdoor air pollution are clear; they have a high cost in mortality and DALYs.  Much of the general public has too vague of an understanding of this relationship, and thus have failed to properly prioritize the issue, particularly in its current context as a soon to emerge critical health problem throughout the world. A public knowledgeable and concerned about outdoor air pollution can stimulate demand for legislation at the local to national levels, providing immediate health and environmental improvements.
Despite the progress that has been made on controlling outdoor air pollution in both the developed and developing world, a tremendous amount of work is left. Increasing funding specifically for research on outdoor air pollution and for related control mechanisms is key to continually developing improved means by which to combat outdoor air pollution. Much of current control strategies work on sources (stationary, mobile, and area) themselves, such as catalytic converters on automobiles, electrostatic precipitators and particulate scrubbers which filter pollutants from gas emissions at the source.  Costs will rise as more are needed to effectively manage and regulate outdoor air pollution, and funding for research must keep scientists employed on projects looking to make such control technology, more efficient and effective, and thereby more affordable. Scientists, health, and environmental professionals have particularly important roles in researching outdoor air pollution and expanding current knowledge eon it. Increased funding will allow for the conducting and publication of more, thorough studies, thereby further expanding the means by which communities throughout the world can respond to outdoor air pollution.  They should also seek to enthusiastically pursue interventions to discover which programs yield the best results.  This group of professionals should also seek to use its expertise to pursue learned advocacy that could optimally impact their communities. 
Outdoor air pollution represents one of the greatest environmental challenges in the upcoming era. The planet is now at a strategic transition point in which many nations are growing rapidly in population, economic development, industrial capacity, and consumption; all nations across the globe will feel the effects of such change within half a century. Outdoor air pollution has the potential to drastically increase its already great burden on human health. Only through immediate, aggressive, and coordinated action can nations expect to cope effectively with the projected health and economic burden of outdoor air pollution. Even more importantly, the initiation of successful policies addressing outdoor air pollution now would establish the precedent for international action on other problems of global scale for the future. Outdoor air pollution represents a grave threat to human health and success, but also represents an opportunity for the nations of the world to truly establish an international community capable of functional cooperation on divisive global issues, and to emerge ready to tackle even greater problems to come.
PLEASE NOTE: Figures included in the essay below were not able to be posted to the website
Fig.1 Chemical outdoor air pollutants vs. source. List is not exhaustive, and does not include biological and other known agents, but serves to illustrate the ubiquity of polluting agents and sources. Above chemical agents are important pollutants with known and documented impacts on human health.
Fig 2. Selected chemical outdoor air pollutant vs. short term and long term human health impacts. 
Fig.3: Projections for real GDP to 2050.  OECD is the Organization for Economic Cooperation and Development, BRIICS are the nations Brazil, Russia, India, Indonesia, China, South Africa, RoW is the rest of the world. Source: OECD Environmental Indicators, Modeling, and Outlook. 
Fig. 4 Estimated deaths attributable to outdoor air pollution versus region of the world, 2004.  Source: WHO Public Health and Environment. [PHE] Eastern Mediterranean omitted for brevity. 
Fig.5: Global Premature Deaths based on particular environmental risks, by 2050.  Source: OECD Environmental Outlook Baseline 
Figure 6: Evolution of the United States’ Clean Air Acts 1955-1990  Source: EPA: History of the Clean Air Act 
Figure 7: Percent Change in Air Quality (United States) based on decade and particular pollutant.  Demonstrates the long term impact of serious legislation (i.e. the Clean Air Acts) and continual updates to expand and broaden its scope. Figure provides a broad indicator of a marked decline in several key areas of outdoor air pollution levels in the United States.
Source: EPA Air Quality Trends 
Figure 8: Partner figure to figure six. US national emissions estimates of selected pollutants based on decade and measured by millions of tons per year.  Demonstrates the potential long term impact of serious legislation to curb and regulate emissions of pollutants in the United States. It is important to target both the general levels of outdoor air pollution and the sources of emissions, reflecting the necessary multipronged approaches of any serious solution to the issue.
Figure 9: United States: comparison of growth areas and emissions, from 1970-2011.  Important to note is the steady increase in population, GDP, and vehicle miles traveled against aggregate emissions.
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